Auxiliary pump for free-piston units



2 Sheets-Sheet 1 W. A. LEDWITH AUXILIARY BUMP FOR FREE-PISTON UNITS 0 R 0 cm 2 M 2. m we mm E v V 1 3 N m6 mw l 0 0.0 f P0 0 Q OQVO n \J 060 O A, 0 r 0 0 P r r 0 0 0 0 w m Q Q Q .VN t

Jan. 4, 1949.

Filed Aug. 23, 1944 AUXILIARY PUMP FOR FREE-PISTON UNITS Patented Jan. 4, 194% AUXILIARY PUMP FOR FREE-PESTON UNITS Walter A. Ledwith, Hartford, Coma, assignor to United Aircraft Corporation, East Hartford, Conn, a corporation of Delaware Application August 23,1944, Serial No. 550,339

This invention relates to free-piston units and particularly to a balance pump forming an mtegral part of the unit.

In certain installations, the starting or control of the free-piston unit may require a supply of high pressure fluid. A feature of this invention is an auxiliary pump operating as a part of the unit and which will maintain a supply of fluid under pressure, thereby eliminating the necessity for an auxiliary supply.

In starting the free-piston unit, some starting systems require that the pistons be moved into starting position, either manually or mechanically, beforethe starting piston functions. Another feature of the invention is an auxiliary device forming a part of the unit by which the pistons may be automatically moved into starting position by fluid under pressure. Another feature is the use of this fluid actuated piston-moving device, during operation of the unit, as a source of fluid under pressure.

Internal cooling of the piston assemblies may be desired in some units. A feature of this invention is the formation of coolant guiding means as a part of the piston-moving device. Another feature is the arrangement of the coolant uiding means as a pump to assist the flow of coolant through the piston.

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate an embodiment of the invention.

Fig. l is a sectional view through the unit.

7 Claims. (Ci. 230-56) Fig. 2 is a fragmentary sectional view of the auxiliary pump.

The unit shown includes an engine cylinder l0 having reciprocating pistons 12 and M to which compressor pistons I6 and I8 in cylinders 20 and 22 are integrally connected. Sleeves 24 and 28 attached to the compressor pistons complete the reciprocating piston assemblies. The sleeves in combination with stationary pistons 28 and 30 form air spring cylinders. I

The piston assemblies are moved apart by'the burning of fuel injected into engine cylinder I!) through one or more nozzles 32. in the air sprin cylinders on the power stroke returns the piston assemblies. The assemblies are always maintained at equal distances from the center of the engine cylinder by a linkage.

Intake manifold 42 which extends around the compressor and engine cylinders, conducts air to intake valves 44 in the heads of the compressor cylinders through which air alternately enters opposite ends of the cylinders. The compressed air leaves the cylinders through discharge valves Air' compressed it, also at opposite ends of the compressor eylin-= ders and passes into a central scavenge chamber 63 and end chambers 58 and 52. These chambers may be interconnected by a scavenge manifold, not shown.

Compressed gas from the scavenge chambers enters engine ports 5&1 and 56 which are uncovered by pistons 52 and it at the end of the power stroke, thereby permitting air to be blown through the engine cylinder. Gas in the engine cylinders isdischarged through exhaust ports 58 into exhaust manifold 60,

Coolant is circulated through each piston assembly, and a supply of gas under pressure is provided during the operation of the unit by the device shown in Fig. 2; Although only one of these devices is shown it will be understood that for purposes of balance two devices may advantageously be used at diametrically opposite points on each piston assembly. Only one device will be described.

Projecting from piston I6 is a tube 62 which flts over a stationary tube 66, the latter having a head 66 by which it is clamped in a bracket 68 which may be a projection on a part of the wall of the scavenge chamber 48. Coolant is admitted to tube 84 through a passage 10 in the bracket and reaches a passage 12 in piston l5 through connecting passages 14 in a cap 16 in the piston. Tube 62 may be screwed into the cap, as shown.

A check valve 18 in the pipe leading to passage 10 prevents back flow of coolant through the passage and as the piston lli moves to the right, thereby decreasin the open space within the tubes 62 and 6t, coolant is forced into passage 12 and through cooling chambers within the piston assembly. A similar pair of tubes, not shown, permits the discharge of coolant from the piston assembly, the check valve being oppositely mounted in the other pair of tubes;

Cooperating with the coolant pumping tubes is a pump for supplying gas under pressure to the unit. A sleeve 82 surrounds tube 62 and may be connected to piston it by engagement with cap 16. As shown, sleeve 82 has a projecting flange 84 which serves to clamp the cap in position in intake valves 44 and the other end of the sleeve is clamped against bracket 88 by a ring 92. Bracket 58 has-an inlet passage 94 communicating with the space between tube 66 and sleeve 88 and a discharge passage 96 also communicating with. this space. Suitable check valves, not shown, control the intake and discharge of gas to this space which by reason of the reciprocation of the piston functions as a pump. It will be understood that passage 94 may be connected to any desired source of gas and passage 96 may be connected to a pressure tank or to any part of the unit which may require a supply of gas under pressure such as the air spring.

The pump, of which there may be more than one for each piston assembly in order to avoid unbalanced forces on the piston, may also be used for cranking the piston assemblies as described in the copending Cooper application, Serial No. 550,875, flied August 23, 1944, now Patent No. 2,439,453. For this purpose sleeve 88 may have an integral boss 98 adjacent to valve M which may be connected to a part of the starting system. When the device is used for cranking the pistons, air under pressure is admitted through passage 94 to the space between tube 64 and 88 moving the piston toward the left until the end of sleeve 82 uncovers the opening I in boss 98, thereby permitting the pressure fluid to pass through opening Hi0 and actuate a supply valve, not shown, by which to cause operation of the starting system. The particular valving by which the starting system is operated is shown in detail in the above identified Cooper application, and since it isnot a part of this invention it will not be described in detail.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

, I claim:

1. A free-piston unit including an engine cylinder and piston, a compressor cylinder and piston, the compressor and engine piston forming a free-moving piston assembly, an air spring cylinder and piston one of which is movable with the piston assembly and the other of which is connected to the engine and compressor cylinder, and an auxiliary cylinder and piston, one of which is connected to the piston assembly and the other of which is connected to one of said engine and compressor cylinders, and means for admitting fluid under pressure to one end of the auxiliary cylinder for moving the piston assembly with respect to the engine and compressor cylinders.

2. A free-piston unit including an engine cylinder and piston, a compressor cylinder and piston, the compressor and engine piston forming a free-moving piston assembly, an air spring cylinder and piston one of which is movable with the piston assembly and the other of which is connectedto the engine and compressor cylinder, an auxiliary cylinder and piston, one of which is connected to the piston assembly and the other of which is connected to one of said engine and compressor cylinders, and means for admitting fluid under pressure to one endof the auxiliary cylinder for moving the piston assembly with reing a piston assembly, a hydraulic pump including an annular plunger and a cylinder in which the plunger is movable, one of said parts being connected to the piston assembly, and a tube fitting Within and slidably engaging said plunger, to form a chamber, and connections from said chamber to the interior of the piston assembly for admitting fluid to said piston assembly.

4. A free-piston unit including an engine cylinder and piston, a compressor cylinder and piston, said pistons forming a piston assembly, and a pump assembly operated by reciprocation of the piston assembly, said pump assembly including an outer cylinder, and an annular plunger within said cylinder, one of said last elements being connected to the piston assembly to reciprocate therewith, and a tube extending centrally of said cylinder, said tube'fltting within and slidably engaging the annular plunger and defining two pumping chambers, one within the tube and the other surrounding the tube.

5. A free-piston unit including an engine cylinder and piston, a compressor cylinder and piston, said pistons forming a piston assembly, and a pump assembly operated by reciprocation "of the piston assembly, said pump assembly including an outer cylinder, and an annular plunger within said cylinder, one of said last elements being connected to the piston assembly, and a tube extending centrally of said cylinder, said tube fitting within the annular plunger, said tube defining pumping chambers, one within and one outside of said tube, one of said chambers having fluid connection with the interior of the piston assembly for circulating fluid through the piston assembly.

6. A free-piston unit including an engine cylinder and piston, acompressor cylinder and piston, said piston forming a piston assembly, and a pump assembly operated by reciprocation of the piston assembly, said pump assembly including an outer cylinder, an annular plunger within said cylinder, one of said last elements being connected to the piston assembly, and a tube extending centrally of said cylinder, said tube fit ting within the annular plunger, said tubedefining pumping chambers, one within and one outside of said tube, one of said chambers having fluid connection with the interior of the piston assembly for circulating fluid through the piston assembly, the other chamber functioning as a chamber for supplying an auxiliary fluid under pressure for the unit.

7. A. free-piston unit including an engine cylinder and piston, a compressor cylinder and piston, said pistons forming a piston assembly, a pump assembly operated by a reciprocation ofv the piston assembly, said pump assembly including an outer cylinder, an annular plunger within said cylinder, one of said last elements being connected to the piston assembly, and a tube extending centrally of said cylinder, said tube fitting within the annular plunger, said tube defining pumping chambers, one within and one outside of said tube, one of said chambers having fluid connection with the interior of the piston assembly for circulation of fluid through the piston assembly, the other chamber functioning by the admission of fluid under pressure thereto for moving the plunger within -the outer cylinder, and thereby moving the piston assembly.

WALTER A. LEDWITH.

(References on following page) REFERENCES CITED Number The following references are of record in the file of this patent. 2,306,978 UNITED STATES PATENTS 5 2,361,316 Number Name Date 2'387'603 129,631 Waring July 16, 1872 255,116 Rand Mar. 21, 1882 N b 314,218 Bolton Mar.24,1885 5 1 694,078 Ritchie- Feb. 25, 1902 541'779 2,007,305 Pateras-Pescara July 9, 1935 2,079,289

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